The overall goal of the proposed research is to provide quantitative understanding of the relationship between neural activity in the primate visual cortex (V1) and behavioral performance in pattern detection tasks. To achieve this goal, monkeys will be trained to perform a demanding visual detection task. While the monkey performs this task, we will use optical imaging with voltage sensitive dyes in conjunction with electrophysiology, to monitor neural population activity in V1. Detailed understanding of the relationship between neural responses in V1 and behavioral performance in this task necessitates explanations of the relationships between three sets of variables: the visual stimuli, neural responses in V1, and the subject's psychophysical performance on the detection task. Our first two aims focus on two fundamental causal relationships between these three variables. In Aim #1 our goal is to determine how visual information regarding the target and the background is represented by populations of V1 neurons. We will address three primary questions: (i) what is the quality of the signals that are provided by V1 to the rest of the visual system, (ii) how is this information distributed in V1, and (iii) what is the optimal way to extract this information from V1? To form a decision regarding the presence or absence of the target, neural circuits subsequent to V1 must 'read out'and interpret the neural signals provided by populations of V1 neurons. Our goal in Aim #2 is to determine which neurons in V1 contribute to the perceptual decision regarding the presence of the target, and how their signals might be pooled to form this decision. Finally, these two fundamental relationships - the encoding of visual information by V1 neurons, and the decoding of V1 responses by subsequent processing stages - may change, depending on the behavioral task. In Aim #3, we propose to vary the task by changing target uncertainty. We will examine the effects of target uncertainty on both behavioral responses and neural responses in V1.